The invention relates to a screen plate, comprising a support frame with support profiles and screen linings made from a rubber elastic material arranged in field-like and detachable manner thereon and which are fixed in locking manner between adjacent support profiles by ledges arranged on their facing end faces and projecting downwards over their underside.
Screen plates or sieve bottoms of the aforementioned construction are e.g. used in the working up of mineral building materials and in particular in the classification of mineral bulk materials. They comprise a substructure in the form of a support frame, which is vibrated by an unbalance drive, as well as several screen fields, which are interchangeably fitted to the substructure and which can be individually replaced in the case of wear.
The main problem in connection with such screen plates is the fixing of the screen linings to the substructure, because the fastening must on the one hand absorb the high dynamic loads and the deformation forces resulting from these and also the applied loads, but must on the other hand ensure a simple and rapid fitting and removal of individual screen linings. For this purpose special support profiles are provided on the substructure and receive the screen linings.
In the known screen plates, the support profiles have through holes, slots or upwardly open cavities, e.g. in the manner of a U-profile with drawn in legs. Adjacent screen linings are provided on their end faces with reciprocally supplementing pins or ledges, which are in each case driven from above into a through hole or cavity and are locked by suitable undercuts. The end faces of the screen linings and the pins or ledges are located in one plane (DE-C 36 06 854). Instead of this, it is also known (DE-A 27 06 277) to interconnect the screen linings by tooth-like construction of their end faces and to lock same to a solid support profile by mutually supplementing recesses on the underside. In another known construction (DE-C 26 22 709, DE-A 26 32 511, 27 49 489) between adjacent screen linings are additionally driven bolts, clamping ledges, etc., which brace the ledges or pins on the screen linings within the slots, through holes or cavities on the support profiles. In all the known constructions either special support profiles are required, or additional fixing means (bolts, clamping ledges) are needed. Considerable difficulties and a large amount of force is required for fitting and removing the screen linings and it is unavoidable that on lifting out one screen lining, the adjacent screen lining will also be loosened.
The aim underlying the invention essentially resides in providing a screen plate, which only requires the simplest standard profiles for the substructure and permits an easy fitting and removal of the screen linings.
In the case of the aforementioned screen plate, the invention is characterized in that the support profiles are constructed as I-profiles and that the ledges of the screen linings have on their facing outsides in each case a slot engaging or gripping over the beam of adjacent I-profiles from the free edge thereof, the width of each screen lining measured on the slot bottom being at least zonely somewhat larger than a clear width between the beams of adjacent I-profiles.
The invention gives the advantage that inexpensive series-produced profiles in the form of I-profiles can be used and are fixed to the substructure. The I-profile beams are used for anchoring the screen linings, in that in each case one screen lining with its frontal ledges is inserted between the I-profiles and the ledges spring inwards due to their rubber elasticity and lock with their slot over the I-beams, so that the screen lining is horizontally and vertically fixed. As a result of the at least zonely larger width of the screen linings in the slot bottom, the screen linings are secured between the I-profiles and, as a function of the oversize quantity, are also pretensioned or prestressed. The removal, like the fitting of the individual screen linings can easily take place by levering out or driving in, which ensures that always only the desired screen lining is detached or, on fitting, each screen lining can be individually fixed.
It is admittedly known in the case of hard metal screens, to fix the screen linings with brackets located on the bottom to the beams of the T-profiles, but the screen linings must then be successively engaged from the side (DE-C 2 417 483).
According to a preferred embodiment of the invention, the ledges are inwardly and downwardly displaced with respect to the end faces of the screen lining and the adjacent screen linings resting on the top of the beams of the I-profiles are in contact with the end faces and terminate flush with one another.
As a result of the above construction, the advantage is obtained that all the fastening means are located below the actual screen surface and consequently little screen surface is lost for this purpose. It is also advantageous for the support profiles are completely covered with respect to the screen feed and are consequently subject to no wear and also a through screen surface is obtained, so that the screen feed can migrate from the feed to the discharge end without obstacles (gaps or the like) in the vicinity of the joints of the screen linings and also no screen feed can penetrate between said linings.
According to another embodiment, the width of the screen linings measured on the slot bottom is over the entire length somewhat greater than the clear width between the beams of adjacent I-profiles, so that there is a firm fixing or pretensioning over the entire width. This can optionally be further increased in that the facing end faces of the screen linings are snugly fitted above the I-profile beams and optionally under a slight pretensioning of the individual screen linings.
An advantageous embodiment is characterized in that the ledges on their back surface remote from the slot are supported via spaced, integral angle brackets on the underside of the screen lining.
The angle brackets ensure that the resiliency of the ledges is reduced or eliminated at certain points of the screen lining, so that the ledge is securely locked to the beam of the I-profiles over the entire length. These angle brackets also ensure a punctiform supporting or pretensioning.
The same function, as well as the stiffening of the screen linings in their plane is served by the measure that, at right angles to the ledges, the screen lining has through reinforcing ribs and that the angle brackets are located in the vicinity thereof.
As a result of the aforementioned construction, the individual screen lining is additionally stiffened and under load a curving up or through is prevented. This can be further assisted in that the screen lining is provided with a reinforcement passing between the end faces and optionally the screen lining can additionally be provided with a steel reinforcement positioned in the reinforcing ribs.
The further measure that the ledges are provided on their outside with insertion bevels facing the I-profiles further simplifies the fitting of the screen lining.
A preferred embodiment of the invention is characterized in that in each case one ledge of each screen lining has a deeper slot than the other ledge and by the deeper slot the screen lining can be laterally mounted on the beam, while the other ledge can be mounted from above on other I-profile. The slot on the one ledge of the screen lining can have a depth substantially corresponding to the width of the I-profile beam over which it engages.
In this embodiment, the screen lining with the deeper slot is engaged on one support profile and is only resiliently locked on to the other support profile with the facing ledge or its slot. This considerably facilitates fitting, because the screen lining is fixed on one side and only has to be driven in on the other side. Conversely, on disassembly, the advantage is obtained that the screen lining only has to be lifted out on one side, whereas it remains fixed on the other side and is subsequently laterally drawn off. This is particularly advantageous if there are fittings, such as spraying devices and the like above the screen surface.
According to a further advantageous development, the ledges are drawn down close to the support frame while laterally covering the support profile. This construction leads to the major advantage that the support profile, including its fastening to the support frame, is protected against the screen feed passing through the screen lining and its abrading action, so that the life becomes substantially unlimited.